/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.confignode.procedure.store;

import org.apache.iotdb.confignode.procedure.Procedure;
import org.apache.iotdb.tsfile.utils.PublicBAOS;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;

public class ProcedureWAL {

    private static final Logger LOG = LoggerFactory.getLogger(ProcedureWAL.class);

    private static final String TMP_SUFFIX = ".tmp";
    private static final int PROCEDURE_WAL_BUFFER_SIZE = 8 * 1024 * 1024;
    private IProcedureFactory procedureFactory;
    private Path walFilePath;

    public ProcedureWAL(Path walFilePath, IProcedureFactory procedureFactory) {
        this.walFilePath = walFilePath;
        this.procedureFactory = procedureFactory;
    }

    /**
     * Create a wal file
     *
     * @throws IOException ioe
     */
    public void save(Procedure procedure) throws IOException {
        File walTmp = new File(walFilePath + TMP_SUFFIX);
        Path walTmpPath = walTmp.toPath();
        Files.deleteIfExists(walTmpPath);
        Files.createFile(walTmpPath);
        try (FileOutputStream fos = new FileOutputStream(walTmp);
             FileChannel channel = fos.getChannel();
             PublicBAOS publicBAOS = new PublicBAOS();
             DataOutputStream dataOutputStream = new DataOutputStream(publicBAOS)) {
            procedure.serialize(dataOutputStream);
            channel.write(ByteBuffer.wrap(publicBAOS.getBuf(), 0, publicBAOS.size()));
        }
        Files.deleteIfExists(walFilePath);
        Files.move(walTmpPath, walFilePath);
    }

    /**
     * Load wal files into memory
     *
     * @param procedureList procedure list
     */
    public void load(List<Procedure> procedureList) {
        Procedure procedure = null;
        try (FileInputStream fis = new FileInputStream(walFilePath.toFile());
             FileChannel channel = fis.getChannel()) {
            ByteBuffer byteBuffer = ByteBuffer.allocate(PROCEDURE_WAL_BUFFER_SIZE);
            if (channel.read(byteBuffer) > 0) {
                byteBuffer.flip();
                procedure = procedureFactory.create(byteBuffer);
                byteBuffer.clear();
            }
            procedureList.add(procedure);
        } catch (IOException e) {
            LOG.error("Load {} failed, it will be deleted.", walFilePath, e);
            walFilePath.toFile().delete();
        }
    }

    public void delete() {
        try {
            Files.deleteIfExists(Paths.get(walFilePath + TMP_SUFFIX));
            Files.deleteIfExists(walFilePath);
        } catch (IOException e) {
            LOG.error("Delete procedure wal failed.");
        }
    }
}
